Plant recognizes others and warns of danger, study reveals

Sagebrush communicated and cooperated with other branches of themselves to avoid being eaten by predators. Scientists suspect that the plants communicate and warn by emitting volatile cues. Are plants capable of more sophisticated behavior than we think?

The research, led by Richard Karban of the U.C. Davis Entomology department, was conducted in conjunction with Kaori Shiojiri of the Center for Ecological Research, Kyoto University, Japan.

Sagebrush responded to cues of self and non-self without physical contact. Air contact, however, was needed for communication to occur.

To test, scientists first covered some sagebrush with plastic bags, thus blocking outside air. Then, plants were sheared (herbivore damage) to mimic the result of an herbivore (such as a grasshopper) eating. In response, volatile cues were released from the cut plant for up to three days. The same response was true when naturally occurring herbivores ate part of the plant. Plants within 60 centimeters of an experimentally clipped neighbor in the field experienced less leaf damage over the season, compared with those near an unclipped neighbor. Plants with root contact between neighbors, but not air contact, did not exhibit any change in leaf damage.

Plants engage in self-recognition and can communicate danger to their “clones” or genetically identical cuttings planted nearby. Plants not only respond to reliable cues in their environments but also produce cues that communicate with other plants and with other organisms, such as pollinators, seed disperses, herbivores and enemies of those herbivores. This observation suggests that communication between individuals may be a by-product of a volatile communication system that allows plants to integrate their own systemic physiological processes. - Richard Karban

The study entitled “Self-Recognition Affects Plant Communication and Defense” is in the current edition of Ecology Letters, and can be found online.